The qubit 
can be represented as a point 
on a unit
sphere called the Bloch sphere. Define the angles 
and 
by letting 
and 
. Here, 
is taken to be real, which can always be made real by multiplying
by an overall phase factor (that
is unobservable). Then 
is represented by the unit vector (
, 
, 
) called the Bloch vector.
Bloch Sphere
See also
Bloch Vector, QubitThis entry contributed by David Terr
Explore with Wolfram|Alpha
References
Nielsen, M. and Chuang, I. Quantum Computation and Quantum Information. Cambridge, England: Cambridge University Press, 2000.Referenced on Wolfram|Alpha
Bloch SphereCite this as:
Terr, David. "Bloch Sphere." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/BlochSphere.html